Integrated circuit (IC) devices, such as memory controllers and memory devices, typically transmit and receive information synchronous with clock signals. For example, transitions of a clock signal indicate that valid information is available on a signal line or set of signal lines coupled to an IC device. Thus, IC devices operate under the constraints of a set of timing parameters so that information transfer may be synchronized according to the clock signals.
For example, an IC device typically has a specified input setup time (tS) and input hold time (tH). Input data should be present and stable on the device input pins from at least tU before a corresponding clock transition and until at least tH after the clock transition for proper operation. Also, the IC device typically has a specified minimum propagation time from clock to output (tCKQ). Output data is valid on the output pins of the device at least tCKQ after the clock transition and should remain valid until a time tV after a next clock transition.
The input and output timing parameters of an IC device typically need to be tested to ensure proper operation of the device in a high speed system. To test an IC device, test equipment accesses the input and output pins of the IC device. Such access may be difficult when the IC device is directly attached to another IC device. For example, an IC memory device may be directly attached to an IC memory controller device such that neither the pins of the memory device nor the pins of the controller device are accessible to test equipment. It would be desirable, therefore, that IC devices in a directly attached configuration are designed to allow their input and output parameters be tested.